Push-pull power amplifier circuit
AssigneeHitachi, Ltd.
InventorKunio Seki
Life of this patent
Estimating the term…
Abstract
A push-pull power amplifier circuit has a supply voltage ripple removing filter connected to a first amplifier stage which includes a first load circuit. A push-pull output stage is composed of at least an output driver and amplifier portion connected to the supply voltage through a second load circuit and an output amplifier portion driven by the output signal of the output driver and amplifier portion as produced in the second load circuit. The second load circuit is provided as a variable impedance which is controlled by a voltage derived from the supply voltage ripple removing filter to prevent operation of said output amplifier portion prior to operation of said first amplifier stage subsequent to switching on of the power supply so as to avoid a "pop" noise being generated in the output of the amplifier.
Claims22
A push-pull power amplifier circuit comprising at least supply voltage ripple removing means;
- first-stage bias means;
- a first amplifier stage which is composed at least of a firststage amplifying element having an input electrode, an output electrode and a grounding electrode, and first load means, a pushpull output stage which is composed at least of an output driver and amplifier portion, second load means, and an output amplifier portion tending towards conduction with decrease in a drive signal current of said output driver and amplifier portion;
- a supply voltage feed terminal;
- and an output terminal;
- said supply voltage ripple removing means and said first-stage bias means being connected in series between said supply voltage feed terminal and ground potential;
- said input electrode of said first-stage amplifying element being connected to said first-stage bias means;
- first and second terminals of said first load means being respectively connected to said supply voltage feed terminal and said output electrode of said first-stage amplifying element;
- said output driver and amplifier portion being connected between said output terminal and ground potential;
- said output driver and amplifier portion and said second load means being connected in series between said supply voltage feed terminal and ground potential;
- said output amplifier portion being connected between said supply voltage feed terminal and said output terminal;
- said output driver and amplifier portion being driven by an output signal of said first amplifier stage as produced in said first load means;
- said output amplifier portion being connected to said second load means and being driven by an output signal of said output driver and amplifier portion as produced in said second load means;
- whereby said output driver and amplifier portion and said output amplifier portion perform a push-pull operation and deliver push-pull output signals to said output terminal;
- said second load means being provided as a variable impedance means responsive to a voltage generated in said supply voltage ripple removing means to provide an impedance prior to operation of said first amplifier stage for preventing operation of said output amplifier portion.
A push-pull power amplifier circuit comprising at least supply voltage ripple removing means, first-stage bias means;
- a first amplifier stage which is composed at least of a first-stage amplifying element having an input electrode, an output electrode and a grounding electrode, and first load means;
- a push-pull output stage which is composed at least of an output driver and amplifier portion, second load means, a first output amplifier portion tending towards conduction with decrease in a drive signal current of said output driver and amplifier portion, and a second output amplifier portion tending towards conduction with increase in said drive signal current;
- a supply voltage feed terminal;
- and an output terminal;
- said supply voltage ripple removing means and said first-stage bias means being connected in series between said supply voltage feed terminal and a ground potential;
- said input electrode of said firststage amplifying element being connected to said first-stage bias means;
- first and second terminals of said first load means being respectively connected to said supply voltage feed terminal and said output electrode of said first-stage amplifying element;
- said output driver and amplifier portion and said second load means being connected in series between said supply voltage feed terminal and said ground potential;
- said first output amplifier portion being connected between said supply voltage feed terminal and said output terminal;
- said second output amplifier portion being connected between said output terminal and said ground potential;
- said first and second output amplifier portions being both driven by an output signal of said driver and amplifier portion, thus to perform a push-pull operation and to deliver push-pull output signals to said output terminal;
- said second load means being provided as a variable impedance means connected to the input of said output amplifier portion and responsive to a voltage generated in said supply voltage ripple removing means to provide an impedance prior to operation of said first amplifier stage for preventing operation of said output amplifier portion.
The push-pull power amplifier circuit according to clain 12, wherein said grounding electrode of said first-stage amplifying element is connected to ground potential.
Dependencies are inferred from the claim text.